Normally a mobile communication system has been developed so as to offer a communication based on user's mobility. With related technologies advanced rapidly, a mobile communication system has reached a stage to provide a high-speed data communication service as well as a voice communication.
Recently 3GPP (3rd Generation Partnership Project) has been discussing the standard of LTE (Long Term Evolution) which is one of next-generation mobile communication systems. LTE technology realizes a high-speed packet based communication that has a transmission rate up to about 100 Mbps which is higher a currently available data transmission rate. Typically discussed for this is an approach to reduce nodes disposed on channels through a simplified network structure or an approach to make wireless protocols be maximally close to wireless channels.
However, despite such efforts, it is still difficult to satisfy increasing users' demands by using limited wireless channel resources. Especially, due to the advent of smart phones, user saturation in a data communication network becomes more and more higher. In view of such situations, mobile communication operators try to solve the saturation of a data network by utilizing a non-3GPP access network, such as a wireless LAN, WiFi, or IEEE 802.11 family, which allows a user's wireless access through the ISM (Industrial Scientific Medical) band. Namely, a part of user's traffic is transmitted using a non-3GPP access network, e.g., an AP (Access Point) of a wireless LAN, rather than to a 3GPP access network through a base station. In this case, an operator can cope effectively with a rapid increase in data by using a frequency band of a non-3GPP access network as well as a frequency band of a 3GPP access network.
In order to offer a policy for selectively using a 3GPP access network, i.e., LTE, and a non-3GPP access network to UE, 3GPP defines ANDSF (Access Network Discovery and Selection Function). This will be described hereinafter with reference to FIG. 1.
FIG. 1 is a schematic diagram illustrating a typical network structure using UE and ADNSF.
Referring to FIG. 1, ANDSF communicates with UE through the S14 interface operating on the IP (Internet Protocol) layer and offers a policy associated with a selection of 3GPP and non-3GPP access networks to UE. Both UE and ANDSF employ the S14 interface on the IP layer in order to send or receive data formed of MO (Management Object) of OMA DM (Open Mobile Alliance Device Management). The IP layer connection between UE and ANDSF is offered by a 3GPP or non-3GPP access network. Additionally, to communicate with ANDSF, UE should create a secure tunnel first of all by using a separate security method. Such requirements may cause an increase in time required to offer a policy from ANDSF to UE. This means that a policy of ANDSF is not sufficient to consider dynamically changed status of UE or access network.